Spark plug assembly with tapered seat

Abstract

The invention relates to a spark plug assembly (10) for a gas engine, comprising a spark plug (16) and a spark plug sleeve (18), where a seat (26) between the spark plug (16) and the spark plug sleeve (18) has a tapered shape.

Description

TECHNICAL FIELD

[0001] The present invention relates to a gas fuel operated internal combustion engine, which is equipped with a spark plug assembly. BACKGROUND

[0002] In order to achieve advantageous combustion conditions during operation of a gas engine, it is known to employ a pre-chamber within the cylinder of the engine. This is particularly applicable to large bore engines and engines burning lean fuel air mixtures. Typically, in such a configuration, the air fuel mixture enters the pre-chamber during the compression stroke of the associated cylinder, which is then ignited by a spark plug. By doing so, a flame front is generated, which propagates from the pre-chamber via a flow transmission channel into the main combustion chamber of the associated cylinder, thereby enabling a consistent combustion of the air fuel mixture present in the main combustion chamber.

[0003] For such a gas engine configuration, it is known to use a component called "pre-chamber spark plug", wherein the functions of the pre-chamber and the spark plug are combined in a single unit. Typically, such a pre-chamber spark plug is arranged at the cylinder head of the engine, such that the tip forming the pre-chamber protrudes into and is connected in fluid communication with the main combustion chamber of the associated cylinder.

[0004] Further, in order to mount the pre-chamber spark plug to the cylinder head, it is known to use a spark plug sleeve, also called mounting sleeve. These sleeves, preferably made of a metallic material, can ensure a proper mounting and can be used to remove heat from the pre-chamber spark plug during operation of the engine. In the context of the present invention, the assembly comprising the spark plug and the spark plug sleeve is called "spark plug assembly". Further, the assembly comprising the spark plug sleeve and the pre-chamber spark plug or the spark plug and a separate pre-chamber is called "pre-chamber spark plug assembly".

[0005] Typically, a requirement for such a pre-chamber spark plug assembly is to ensure a sealing and a proper heat conduction between the pre-chamber spark plug and the spark plug sleeve during operation. SUMMARY

[0006] Starting from the prior art, it is an object of the present invention to provide an improved spark plug assembly for a gas engine, which comprises a spark plug and a spark plug sleeve and which improves the sealing and the heat conduction between its components, in particular during operation of the gas engine. Further, it is an object of the present invention to provide a spark plug and a spark plug sleeve for use in such a spark plug assembly.

[0007] The spark plug assembly can comprise a pre-chamber spark plug and / or a spark plug without a pre-chamber and / or a separate pre-chamber.

[0008] These objects are solved by the subject matter of the independent claims. Preferred embodiments are set out in the description, the drawings and the dependent claims.

[0009] Thus, a spark plug assembly, in particular a pre-chamber spark plug assembly, for a gas engine is provided, comprising a spark plug, in particular a pre-chamber spark plug, and a spark plug sleeve, wherein the seat between the spark plug and the spark plug sleeve has a conical shape.

[0010] Further, a spark plug, in particular a pre-chamber spark plug, for such a spark plug assembly, in particular a pre-chamber spark plug assembly, is provided, the spark plug comprising a seat surface configured to abut against a further seat surface of the spark plug sleeve to form a seat between the pre-chamber spark plug and the spark plug sleeve, wherein the seat surface has a conical shape.

[0011] Still further, a spark plug sleeve for such a spark plug assembly, in particular for such a pre-chamber spark plug assembly, is provided, the spark plug sleeve comprising a seat surface configured to abut against a further seat surface of the spark plug, in particular a pre-chamber spark plug, to form a seat between the pre-chamber spark plug and the spark plug sleeve, wherein the seat surface has a conical shape.

[0012] Since the spark plug and the spark plug sleeve are intended for use in the above-mentioned spark plug assembly, technical features described in the following in the context of the spark plug assembly can also relate and apply to the spark plug and the spark plug sleeve, i.e. should be considered as disclosed for the spark plug and the spark plug sleeve, and vice versa. BRIEF DESCRIPTION OF DRAWINGS

[0013] The application will be more readily understood by reference to the following detailed description, taken in conjunction with the accompanying drawings, in which:

[0014] Figure 1 a longitudinal view of a spark plug assembly according to a first embodiment is depicted;

[0015] Figure 2 an enlarged view of the spark plug assembly in a state of disengagement of its components is depicted;

[0016] Figure 3 a spark plug assembly according to a second embodiment is depicted; and

[0017] Figure 4 a spark plug assembly according to a third embodiment is depicted. DETAILED DESCRIPTION

[0018] In the following, the present application will be explained in more detail with reference to the accompanying drawings. In the drawings, identical elements are denoted by identical reference signs, and a repeated description thereof can be omitted to avoid redundancy.

[0019] Figure 1 A spark plug assembly in the form of a pre-chamber spark plug assembly 10 is depicted, which is referred to in the following as "pre-chamber assembly". The pre-chamber assembly 10 is at least partially received in and mounted to a cylinder head 12 of an internal combustion engine, which is also referred to in the following as "engine". The engine is preferably a gas engine. In the context of the present invention, the term "gas engine" generally refers to any internal combustion engine that operates with a gaseous fuel, such as natural gas, biogas, etc. The use of the proposed pre-chamber assembly 10 is not limited to engines of a specific application, but can be applied to different technical fields, such as gas engines used as main engines or auxiliary engines in power plants or vehicles, etc.

[0020] The engine employing the proposed pre-chamber assembly 10 preferably comprises a plurality of cylinders, for example, four, eight, twelve or eighteen cylinders. The cylinders can be arranged in an engine block and can be bounded from above by at least one cylinder head 12. Generally, the cylinder head 12 refers to a component of the engine that is preferably fixed to the engine block and that partially bounds one or more combustion chambers 14 arranged in the cylinders of the engine, which are also referred to in the following as "main combustion chambers".

[0021] Preferably, the engine is equipped with a plurality of pre-chamber assemblies 10, each of which is associated with a different one of the plurality of cylinders. In other words, one pre-chamber assembly 10 is arranged in each cylinder of the engine.

[0022] In the following, the structural and functional configuration of the pre-chamber assembly 10 is described with reference to the depicted embodiment, which can be applied to one or more of the plurality of pre-chamber assemblies 10 used in the engine, preferably to all pre-chamber assemblies 10. Figure 1

[0023] The pre-chamber assembly 10 comprises a pre-chamber spark plug 16 and a spark plug sleeve 18, which is also referred to in the following as "sleeve". The pre-chamber spark plug 16 is at least partially received within the sleeve 18 and is fixed or attached to the sleeve 18, in particular by means of at least one threaded connection 20. Specifically, the pre-chamber spark plug 16 is received within the sleeve 18 such that a first seat surface 22 of the pre-chamber spark plug 16 abuts against a second seat surface 24 of the sleeve 18. By this configuration, the first seat surface 22 and the second seat surface 24 form a seat 26 between the pre-chamber spark plug 16 and the sleeve 18. The sleeve 18 is in turn fixed to the cylinder head 12 by means of a further threaded connection 28.

[0024] ​The pre-chamber spark plug 16 and the sleeve 18 extend along a longitudinal axis L of the pre-chamber assembly 10. The longitudinal axis L of the pre-chamber assembly 10 coincides with the intermediate longitudinal axis of the spark plug 16 and the sleeve 18.

[0025] As can be taken from Figure 1 , the pre-chamber spark plug 16 is fixed to the sleeve 18 via a threaded connection 20, the sleeve 18 is fixed to the cylinder head 12 via a further threaded connection 28, both threaded connections overlapping in direction along the longitudinal axis L. In other words, the threaded connection 20 and the further threaded connection 28 are at least partially arranged at the same height or level with respect to the longitudinal axis L.

[0026] This arrangement is achieved by having the sleeve 18 at its bottom portion, i.e. the portion of the sleeve 18 facing the main combustion chamber 14, a hollow cylindrical shape, which is provided with an inner thread and an outer thread. As can be taken from Figure 1 , the inner thread, hereinafter also referred to as first thread, is configured to engage with a correspondingly designed thread, hereinafter also referred to as second thread, provided at the outer surface of the pre-chamber spark plug 16, which threads together form the first threaded connection 20. The outer thread at the sleeve 18 is configured to engage with a further thread provided at the inner surface of the receiving bore of the cylinder head 12, which threads together form the second threaded connection 28.

[0027] Generally, in the context of the present invention, the terms "lower", "bottom", and the like refer to a position or portion facing or arranged in the vicinity or proximity of the associated cylinder or main combustion chamber 14 of the engine. Accordingly, the term "below" is used in the following to denote a direction pointing towards the associated cylinder or main combustion chamber 14 of the engine, whereas the term "above" or "upwardly" refers to the opposite direction.

[0028] More specifically, the sleeve 18 is designed such that its inner thread and its outer thread extend in upward direction along the longitudinal axis from the bottom end of the sleeve 18, i.e. in direction away from the main combustion chamber 14 along the longitudinal axis L. In the shown configuration, the inner thread extends in upward direction beyond the outer thread.

[0029] The pre-chamber spark plug 16 is configured to combine the functionality of a pre-chamber and the functionality of an ignition element, in particular a spark plug, in a single unit, which can be assembled from several parts. As such, the pre-chamber spark plug 16 comprises a pre-chamber and a spark plug (not shown). The pre-chamber is formed by a pre-chamber cover 30 provided at the tip end of the pre-chamber spark plug 16. In the mounted state of the pre-chamber spark plug assembly 10, as Figure 1As depicted, the pre-chamber cover 30 protrudes into the main combustion chamber 14 and is connected in fluid communication with the main combustion chamber 14 via a plurality of flow transmission channels 32. With this configuration, during engine operation, an air-fuel mixture can enter the pre-chamber within the pre-chamber cover 30 via the flow transmission channels 32, in particular during the compression stroke, which can then be ignited by a spark generated by the ignition element of the pre-chamber spark plug 16. By doing so, a flame front can propagate from the pre-chamber into the main combustion chamber 14 via the flow transmission channels 32, thereby combusting the air-fuel mixture present in the main combustion chamber 14.

[0030] According to one configuration, the pre-chamber spark plug 16 can be designed such that the air-fuel mixture immersed into the pre-chamber during the intake stroke is enriched by feeding a gaseous fuel into the pre-chamber via a separate fuel supply channel. According to an alternative configuration, such separate fuel supply channel can be omitted, such that the air-fuel mixture immersed into the pre-chamber is ignited without being enriched by additional fuel.

[0031] The pre-chamber spark plug 16 can comprise different portions, which can subdivide the pre-chamber spark plug 16 into different portions, in particular along the longitudinal axis L. For example, in the configuration shown, the pre-chamber spark plug 16 can be subdivided into a tip portion 34 and a rear portion (not shown). The tip portion 34 is arranged in a lower portion or lower half of the pre-chamber spark plug 16 facing the main combustion chamber 14. From the tip portion 34, the flow transmission channels 32 extend into the main combustion chamber 14. Figure 1 As can be taken from Fig. 2, the tip portion 34 comprises the pre-chamber cover 30, the second thread forming the threaded connection 20 and the seat 26. As such, the tip portion 34 comprises the pre-chamber.

[0032] The pre-chamber spark plug 16 and the sleeve 18 can be made of the same material. For example, the pre-chamber spark plug 16 and the sleeve 18 can be made of a ferrous material, in particular of steel, such as cast iron or grey cast iron.

[0033] The basic structural and functional configuration of such pre-chamber assembly 10, in particular of its pre-chamber spark plug 16 and sleeve 18, is known to the person skilled in the art and, therefore, is not further described in the present application. Instead, technical features related to the seat 26 and its underlying functionality will be explained in the following, which are interrelated with the present application. Although not further described in the following, it is understood by the person skilled in the art that the pre-chamber spark plug 16 can comprise additional components, such as an insulator, an electrode, a fuel supply channel, etc.

[0034] The seat 26 serves to correctly mount the pre-chamber spark plug 16 within the sleeve 18. As such, the seat 26 can have a sealing function, among others, to establish a seal between the components of the pre-chamber assembly 10. Thus, the seat 26 can also be referred to as a sealing or sealing seat. Further, the seat 26 is preferably used to transfer heat between the components during engine operation, for example to protect the pre-chamber spark plug from overheating.

[0035] It can be seen from Figure 1 that the threaded connection 20 is arranged in the region of the seat 26, in particular in the vicinity of the seat 26. This is achieved by arranging the threaded connection 20 and the seat 26 at or within the tip portion 34 of the pre-chamber spark plug 16. As such, the threaded connection 20 and the seat 26 are arranged in the same half of the pre-chamber assembly 10, namely in the bottom half thereof. In other words, the seat 26 and the threaded connection 20 are arranged within a top half of the pre-chamber spark plug 16 or the pre-chamber assembly 10, which faces the main combustion chamber 14 and which at least partially projects into the main combustion chamber 14, which can also be referred to as a bottom half. The top half can extend along half of the overall length of the pre-chamber spark plug 16 or the pre-chamber assembly 10, along its longitudinal axis L. More specifically, the threaded connection 20 is arranged at a distance d, in particular a minimum distance d, from the seat 26, wherein the distance d is less than 0.1 to 3 times the diameter D of the pre-chamber spark plug 16 at the seat 26. It can be seen from Figure 1 that the diameter D extends perpendicular to the longitudinal axis L. In particular, the distance d can be 0.1 to 3 times the diameter D. Alternatively or additionally, the distance d can be less than the diameter D.

[0036] In comparison to configurations of pre-chamber spark plug assemblies, wherein the threaded connection is provided only at the rear end or rear portion of the pre-chamber spark plug assembly and not in the vicinity of the seat, it has been found that the proposed arrangement can improve the pressure distribution at the seat 26 and, thus, the sealing and heat conduction characteristics of the proposed assembly.

[0037] In the depicted configuration, the pre-chamber assembly 10 is designed such that the threaded connection 20 is arranged behind, i.e. after, the seat 26 along the longitudinal direction, i.e. along the direction of the longitudinal axis L, from the rear end pointing towards the pre-chamber cover 30 of the pre-chamber spark plug 16. In other words, the threaded connection 20 is arranged below the seat 26. In alternative embodiments, as will be described below in connection with Figure 4 the depicted configuration, the threaded connection 20 can be arranged in front of, i.e. above, the seat 26 along the longitudinal direction. In further alternative embodiments, the threaded connection 20 can comprise a first portion arranged in front of, i.e. above, the seat 26 along the longitudinal direction and a second portion arranged behind, i.e. below, the seat 26.

[0038] Reference will be made to Figure 2The structure configuration of the seat 26 is further explained in detail.

[0039] As can be taken from Figure 2 the seat 26 has a conical shape. In other words, the seat 26 has a shape which narrows along the longitudinal axis L of the pre-chamber spark plug 16. In particular, the seat 26 narrows, i.e. its diameter decreases, along a longitudinal direction pointing from the rear end of the pre-chamber spark plug 16 towards the pre-chamber cover 30.

[0040] More specifically, in the illustrated configuration, the seat 26 has a conical shape. In the context of the present summary, the term “conical shape” refers to a shape which follows or represents at least a portion of a shell surface of a cone. As such, the conical shape can refer to a shape which follows or mimics a shell surface of a cone or a truncated cone. However, according to the proposed configuration, the seat can not be limited to a conical shape, but can comprise any suitable conical shape. The conical shape can be a continuously narrowing shape, e.g. having a curved shape or shell surface, or a gradually narrowing shape, e.g. having a stepped shape or shell surface.

[0041] In the illustrated configuration, the seat 26 can have a cone angle γ, which can also be referred to as a taper angle, which is between substantially 75° and substantially 105°, in particular between 79° and 102°. For example, the cone angle γ of the seat 26 can be 80° or substantially 80°, as Figure 1 illustrated. The proposed cone angle can affect, in particular reduce, the minimum release torque required to disengage the pre-chamber spark plug 16 from the sleeve 18 compared to a smaller cone angle. Thus, by this configuration, the assembly or disassembly operation of the installer can be improved.

[0042] As mentioned above, the seat 26 is formed at least by a first seat surface 22 of the pre-chamber spark plug 16 and a second seat surface 24 of the sleeve 18. The first seat surface 22 is provided at an outer surface or shell surface of the pre-chamber spark plug 16. In particular, the first seat surface 22 is provided circumferentially around the longitudinal axis and circumferentially along the outer surface or shell surface of the pre-chamber spark plug 16. The second seat surface 24 is provided at an inner surface of the spark plug sleeve 18, in particular circumferentially around the longitudinal axis thereof and circumferentially along the inner surface of the spark plug sleeve 18. In the illustrated configuration, each of the first seat surface 22 and the second seat surface 24 has a conical shape as Figure 2 depicted.

[0043] Figure 2A disengaged state of the pre-chamber assembly 10 is shown, in which the pre-chamber spark plug 16 and the spark plug sleeve 18 are not fully engaged, such that the first seat surface 22 and the second seat surface 24 are disengaged, i.e. spaced apart from each other. In this state, the first seat surface 20 is inclined with respect to the longitudinal axis of the pre-chamber spark plug 16 by a first inclination angle a, and the second seat surface 24 is inclined with respect to the longitudinal axis of the spark plug sleeve 18 by a second inclination angle b. In the shown state, the longitudinal axis of the pre-chamber spark plug 16 and the longitudinal axis of the spark plug sleeve 18 coincide.

[0044] The first inclination angle a of the first seat surface 22 is smaller than the second inclination angle b of the second seat surface 24. With this configuration, the pressure distribution at the seat 26 can be adjusted such that the seat pressure at a radially inner region of the seat 26 is higher than the seat pressure at a radially outer region. In this way, the proposed arrangement can ensure an improved sealing between the components of the pre-chamber spark plug assembly 10.

[0045] In particular, the difference between the first inclination angle a of the first seat surface 22 and the second inclination angle b of the second seat surface 24 is larger than a tolerance, in particular a manufacturing or component tolerance, of at least one of the first inclination angle a and the second inclination angle b. More specifically, the difference between the first inclination angle a of the first seat surface 22 and the second inclination angle b of the second seat surface 24 is larger than the sum of a tolerance, in particular a manufacturing or component tolerance, of the first inclination angle a and a tolerance of the second inclination angle b.

[0046] More specifically, the difference between the first inclination angle a of the first seat surface 22 and the second inclination angle b of the second seat surface 24 is at least 10° or at least 20° or at least 30° or at least 40°.

[0047] Figure 3 A further embodiment of the pre-chamber assembly 10 is shown. Compared to the depicted configuration, Figure 1 and Figure 2 The seat 26 of the pre-chamber spark plug assembly 10 is additionally provided with a circumferential groove 36, which can also be referred to as a sealing groove, compared to the depicted configuration. By providing the groove 36 on the seat 26, it has been found that the sealing of the seat 26 can be improved.

[0048] More specifically, in the shown configuration, the first seat surface 22 is provided with the groove 36. Alternatively or additionally, the second seat surface 24 can be provided with such a circumferential groove. Thus, the technical features of the groove 36 of the first seat surface 22 described in the following can be applied accordingly to a groove provided in the second seat surface and thus considered to be disclosed.

[0049] The groove 36 extends circumferentially along the first seat surface 22 around the longitudinal axis L. In the illustrated configuration, the groove 36 is arranged in a middle region of the first seat surface 22. That is, along the longitudinal axis L, the groove 36 is arranged spaced apart from the end portion or boundary edge of the first seat surface 22. In other words, the groove 36 divides the first seat surface 22 into two parts, namely, into an upper part 22a and a lower part 22b, as shown in FIG. Figure 3 Alternatively, the groove 36 may be arranged in the vicinity of or adjacent to one of the boundary edges of the first seat surface 22 .

[0050] In the configuration shown, the first seat surface 22 is provided with a single groove 26. In a further development, the first seat surface 22 may be provided with more than one groove 26, for example with two separate grooves.

[0051] Optionally, a sealing element 38 is housed within groove 36. Sealing element 38 may be made of metal or rubber. For example, sealing element 38 may be an O-ring or a sealing tape. Alternatively or additionally, thermally conductive grease or a thermally conductive component may be disposed within groove 36.

[0052] Figure 4 A further embodiment of the pre-combustion chamber assembly 10 is shown. Figure 1 and Figure 2 Compared to the depicted configuration, the threaded connection 20 is arranged before, ie in front of, the seat 26 in the longitudinal direction of the pre-combustion chamber spark plug assembly 10 .

[0053] Also in the illustrated configuration, the threaded connection 20 is disposed at or within the tip portion 34 of the pre-combustion chamber spark plug 16. Specifically, the threaded connection 20 is disposed at a distance d' from the seat 26, particularly at a minimum distance d', wherein the distance d' is less than 0.1 to 3 times the diameter D of the pre-combustion chamber spark plug 16 at the seat 26. Specifically, the distance d' may be 0.1 to 3 times the diameter D. Alternatively or additionally, the distance d' may be less than the diameter D.

[0054] By this arrangement, i.e., by inserting the seat 26 between the threaded connection 20 and the combustion chamber 14, the threaded connection can be protected from combustion products. Furthermore, it has been discovered that by positioning the threaded connection 20 above the seat 26, the threaded connection 20 can be positioned closer to cooling passages disposed in or adjacent to the pre-combustion chamber assembly 10, thereby improving heat transfer from the pre-combustion chamber spark plug assembly 10.

[0055] Further, by this structural configuration, a tip gap 40 is provided, which extends from the seat 26 between the sleeve 18 and the tip portion 34 and opens into the combustion chamber 14. The gap 40 extends circumferentially around the tip portion 34 and has a width, i.e. along the radial direction, of between 0 mm and 1 mm, e.g. 0.5 mm. Alternatively or additionally, the gap 40 can have a width of between 0% and 5% of the diameter D, e.g. 3.5% of the diameter D. In particular, the gap 40 can have a width of between 0% and 1% of the diameter D.

[0056] By arranging the threaded connection 20 above the seat 26, the illustrated configuration can be provided with a gap 40, which can have a smaller width than a configuration in which the threaded connection is arranged below the seat 26. The illustrated structural configuration can thus allow to provide a pre-chamber assembly of a smaller diameter, which can thus contribute to an improved space utilization.

[0057] It will be obvious to a person skilled in the art that the embodiments and items depicted are merely examples of a plurality of possibilities. The embodiments shown here should therefore not be understood as forming limitations to these features and configurations. Any possible combination and configuration of the described features can be selected in accordance with the scope of the present invention. This is in particular the case with respect to the following optional features, which can be combined with some or all of the previously mentioned embodiments, items and / or features in any technically feasible combination.

[0058] In particular, a spark plug assembly for a gas engine can be provided.

[0059] The spark plug assembly can be a pre-chamber spark plug assembly. As such, the spark plug assembly can comprise a pre-chamber spark plug and / or a spark plug without a pre-chamber and / or a separate pre-chamber. As such, the proposed spark plug assembly is not limited to a pre-chamber spark plug assembly.

[0060] The spark plug assembly, in particular the pre-chamber spark plug assembly, can comprise a spark plug, in particular a pre-chamber spark plug, and a spark plug sleeve, wherein a seat between the spark plug and the spark plug sleeve has a conical shape.

[0061] The spark plug can be within the spark plug sleeve and can be fixed to the spark plug sleeve by at least one threaded connection. Further, the spark plug sleeve can be configured to be fixed or mounted at a cylinder head of the gas engine by a further threaded connection, wherein, in particular, the threaded connection and the further threaded connection overlap in a direction along a longitudinal axis of the spark plug assembly.

[0062] Further, the thread connection can be arranged in a region of the seat. For example, the seat and the thread connection can be arranged at a tip portion of the spark plug. The tip portion can comprise a pre-chamber. In particular, the thread connection can be arranged within a distance to the seat, wherein the distance can be 0.1 to 3 times a diameter of the spark plug at the seat, in particular less than the diameter. Alternatively or additionally, the spark plug assembly can be designed such that, in a direction along a longitudinal axis of the assembly pointing from the rear end to the tip portion of the spark plug, the thread connection is arranged behind and / or in front of the seat.

[0063] Alternatively or additionally, the seat can have a conical shape. The seat can have a cone angle between 75° to 105°, in particular 80° or substantially 80°. In a further development, the seat can be formed by at least a first seat surface of the spark plug and a second seat surface of the spark plug sleeve. Optionally, the spark plug assembly can be designed such that, in a disengaged state of the seat in which the first seat surface and the second seat surface are disengaged, i.e. spaced apart from each other, the first seat surface is inclined with respect to a longitudinal axis of the spark plug about a first inclination angle which is smaller than a second inclination angle about which the second seat surface is inclined with respect to a longitudinal axis of the spark plug sleeve. In a further development, a difference between the first inclination angle and the second inclination angle can be larger than a sum of a tolerance of the first inclination angle and a tolerance of the second inclination angle.

[0064] For example, the difference between the first inclination angle and the second inclination angle can be at least 10', i.e. 10 minutes of arc, or at least 20', i.e. 20 minutes of arc.

[0065] Alternatively or additionally, at least one of the first seat surface and the second seat surface can be provided with a circumferential groove. In a further development, the at least one circumferential groove can divide the first seat surface and / or the second seat surface into two portions. Further, at least one of the at least one circumferential groove can accommodate a sealing element, for example an O-ring and / or a sealing band and / or a heat conducting element, such as a heat conducting paste.

[0066] Further, a spark plug, in particular a pre-chamber spark plug, can be provided for a spark plug assembly, in particular a pre-chamber spark plug assembly, as described above, comprising a seat surface configured to abut against a further seat surface of a spark plug sleeve to form a seat between the spark plug and the spark plug sleeve, wherein the seat surface has a conical shape. The seat surface of the spark plug can be a circumferential seat surface of conical shape, in particular a circular conical shape. For example, the seat surface can have a cone angle between 75° to 105°, in particular 80° or substantially 80°. Further, the spark plug can comprise a thread configured to engage with a further thread of the sleeve. The thread can be arranged in or near a region of the seat surface. In a direction along a longitudinal axis of the spark plug pointing to a tip portion thereof, the thread can be arranged before or after the seat surface.

[0067] Alternatively or additionally, the thread can be arranged within a distance from the seat surface, wherein the distance can be less than or can be 0.1 to 3 times the diameter of the spark plug at the seat, in particular less than the diameter.

[0068] Alternatively or additionally, the seat surface can be provided with a circumferential groove, in particular as described above.

[0069] Further, a spark plug sleeve for use in a spark plug assembly as described above can be provided, the spark plug sleeve comprising a seat surface configured to abut against a further seat surface of a spark plug to form a seat between the spark plug and the spark plug sleeve, wherein the seat surface has a conical shape. The seat surface of the sleeve can be a circumferential seat surface of conical shape, in particular of circular conical shape. For example, the seat surface can have a cone angle between 75° and 105°, in particular 80° or substantially 80°. Further, the sleeve can comprise a thread configured to engage with a further thread of the sleeve. The thread can be arranged in or near the region of the seat surface. In a direction along a longitudinal axis of the sleeve, pointing from a rear end having a first diameter to a tip portion having a second, smaller diameter, the thread can be arranged in front of or behind the seat surface.

[0070] Alternatively or additionally, the seat surface can be a circumferential seat surface of conical shape, in particular of circular conical shape, which can be provided with a circumferential groove, in particular as described above.

[0071] Industrial applicability

[0072] With reference to the drawings, a spark plug assembly for a gas engine is suggested. The spark plug assembly as described above is suitable for use in any suitable internal combustion engine. The proposed spark plug assembly can replace a conventional spark plug assembly and can be used as a replacement or retrofit.

Claims

1. A spark plug assembly (10), in particular a spark plug assembly (10) for a gas engine, comprising a spark plug (16) and a spark plug sleeve (18), wherein a seat (26) between the spark plug (16) and the spark plug sleeve (18) has a conical shape.

2. The spark plug assembly according to claim 1 , wherein the spark plug ( 16 ) is received in the spark plug sleeve ( 18 ) and is fixed to the spark plug sleeve ( 18 ) by at least one threaded connection ( 20 ), the threaded connection ( 20 ) being arranged in particular in the region of the seat ( 26 ).

3. The spark plug assembly according to claim 2, wherein the seat (26) and the threaded connection (20) are arranged at a tip portion (34) of the spark plug (16), wherein in particular the tip portion (34) comprises a pre-combustion chamber.

4. A spark plug assembly according to claim 2 or 3, wherein in the direction along the longitudinal axis (L), the longitudinal axis (L) points from the rear end to the tip portion (34) of the spark plug (16), the threaded connection (20) is arranged behind or in front of the seat (26).

5. Spark plug assembly according to any one of claims 2 to 4, wherein the threaded connection (20) is arranged within a distance (d; d') from the seat (26), wherein the distance (d; d') is 0.1 to 3 times the diameter (D) of the spark plug (16) at the seat (26), in particular smaller than the diameter (D).

6. The spark plug assembly according to any one of claims 1 to 5, wherein the seat (26) has a conical shape.

7. Spark plug assembly according to claim 6, wherein the seat (26) has a cone angle (γ) between 75° and 105°, in particular a cone angle of substantially 80°.

8. The spark plug assembly of claim 6 or 7, wherein the seat (26) is formed by a first seat surface (22) of the spark plug (16) and a second seat surface (24) of the spark plug sleeve (18), and wherein the spark plug assembly (10) is designed so that in a disengaged state in which the first seat surface (22) and the second seat surface (24) of the seat (26) are disengaged, the first seat surface (22) is inclined relative to the longitudinal axis (L) of the spark plug (16) by a first inclination angle (α) that is less than a second inclination angle (β) at which the second seat surface (24) is inclined relative to the longitudinal axis (L) of the spark plug sleeve (18).

9. The spark plug assembly of claim 8, wherein a difference between the first inclination angle (α) and the second inclination angle (β) is greater than a sum of a tolerance of the first inclination angle (α) and a tolerance of the second inclination angle (β).

10. The spark plug assembly according to any one of claims 8 or 9, wherein the difference between the first inclination angle (α) and the second inclination angle (β) is at least 10' or 20'.

11. The spark plug assembly according to any one of claims 1 to 10, wherein the first seat surface (22) or the second seat surface (24) is provided with a circumferential groove (36).

12. The spark plug assembly of claim 11, wherein the circumferential groove (36) divides the first seat surface (22) or the second seat surface (24) into two parts (22a, 22b).

13. The spark plug assembly of claim 11 or 12, wherein a sealing element (38) is received in the circumferential groove (36).

14. A spark plug (16) for use in a spark plug assembly (10) according to any one of claims 1 to 13, comprising a seat surface (22) configured to abut against a further seat surface (24) of the spark plug sleeve (18) to form the seat (26) between the spark plug (16) and the spark plug sleeve (18), wherein the seat surface (22) has a conical shape.

15. A spark plug sleeve (18) for use in a spark plug assembly (10) according to any one of claims 1 to 13, comprising a seat surface (24) configured to abut against a further seat surface (22) of the spark plug (16) to form the seat (26) between the spark plug (16) and the spark plug sleeve (18), wherein the seat surface (24) has a conical shape.

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